1. Field of the Invention
The invention relates to a development roller, a development roller base, a development roller manufacturing method, and an image forming apparatus.
2. Description of the Related Art
In an image forming apparatus in which a toner image is formed on a recording medium by the so-called electrostatic recording method, development (visualization) is performed by forming an electrostatic latent image with a laser beam from a light-beam scanning device to supply toner to the electrostatic latent image from a development roller while a photosensitive drum is charged by a charging device. The toner of the visualized image is transferred and fixed to the recording medium such as paper to obtain the desired image on the recording medium.
In the image forming apparatus having the above-described configuration, in order to obtain a high-quality image, it is desirable to narrow a gap between the photosensitive drum and the development roller (hereinafter, the gap is referred to as DRS). However, in this case, bias leakage (voltage leakage) tends to easily occur between the photosensitive drum and the development roller. The bias leakage easily occurs particularly when atmospheric pressure is low as in high altitude areas and the like. The bias leakage causes damage to the photosensitive drum and the development roller and a decrease in quality of the image on the recording medium. For example, it is conceivable that a method of decreasing development bias voltage is employed in order to prevent the voltage leakage. However, a good-quality image can not be obtained by this method due to the decrease in development efficiency.
A configuration in which bias leakage is eliminated by setting DRS and the development bias voltage to a predetermined range is described in Japanese Patent Application Laid-Open (JP-A) No. 5-11582.
However, in the configuration described in JP-A No. 5-11582, it is difficult to prevent the bias leakage when the atmospheric pressure is low as in high altitude areas, and the lower limit of DRS is restricted, so that there is a limitation to obtain a high-quality image by further narrowing DRS to increase the development efficiency.